It is the goal of study to define the role of the alveolar epithelium of the lung in the maintenance of fluid distribution across the barrier between blood and air. Two preparations, the excised amphibian lung and an oil blocked, microlavaged terminal alveolar sac of the rat lung, will be examined. These preparations restrict solute transfer to paths across the alveolar epithelium; parallel routes through the airway eipthelium are excluded. The proposed studies with amphibian lung will extend our earlier work by examining nonelectrolyte, K ion and Ca ion fluxes along with the effects of three groups of environmental pollutants (heavy metals, and ozone product and the dipyridilium herbicides) on bioelectric properties, solute permeability and biochemical indices of free radical production. Micropuncture and oil blockade of a terminal alveolar sac will allow measurement of the transalveolar bioelectric p.d. and solute permeability. Effects of the selected pollutants on these parameters will be explored. Thus, a second objective of this project is to identify the locus and nature of pollutant damage to the air-blood barrier and to relate this damage to metabolic events in the alveolar epithelium.